This invention relates to an image forming apparatus.
Conventionally, from a viewpoint to resource saving, some image forming apparatus such as a printer, e.g., such as described in Japanese Patent Application Publication No. JA-8-367470, has a function for limiting the usable sheet number of recording sheets. The image forming apparatus has a data memory means for memorizing a limited usable number of the recording sheets and a used recording sheet number already printed; a comparison means for making a summation of a printing request sheet number and the used sheet number to compare a summed result with the limited usable sheet number; and a controlling means for controlling to discontinue printing operation of printing data on the recording sheet in a case that as the compared result the limited usable sheet number becomes less than the summed result. The image forming apparatus is set as to return a using rejection message to a host apparatus as a requesting source in a case of receiving a printing request without use right in the printing request from the host apparatus.
The aforementioned conventional image forming apparatus, however, cannot suitably cope with fluctuation in the using sheet number at each predetermined period. The limited usable sheet number is set per the predetermined period, e.g., one month but the using recording sheet number changes at each period. Therefore, the recording sheets remain over or run short from month to month where the restricted using recording sheet number is monthly stabilized. In that case, an administrator monthly needs to adjust the restricted using sheet number. Furthermore, just before an end of the period, i.e., the end of the month, from thought that the prescribed number is to be fully used, unnecessary printing may be performed, so that an primary object to suppress printing performance cannot be achieved.
Until the summed result of the printing request sheet number plus the used sheet number reaches the limited usable sheet number, a host apparatus is informed nothing while informed an unprintable state when the summed result exceeds the printing request sheet number, so the host apparatus cannot grapes in advance when the printing operation becomes unprintable.